Ibragim Todashev was killed in his Florida apartment in the presence of two Massachusetts state troopers during questioning surrounding Marathon bombing suspect Tamerlan Tsarnaev.

According to court documents released in October, federal prosecutors acknowledged that Todashev, Tsarnaev’s friend, told authorities that Tsarnaev participated in the 2011 triple homicide in Waltham.

Todashev's father, Abdulbaki Todashev, has released an open letter to President Barack Obama that includes photos of Todashev's bloody apartment and photos of his son taken at the morgue, according to Wicked Local news partner WCVB. He said the FBI tortured and deliberately killed his son.

Todashev says his son voluntarily went to an FBI office in Orlando to speak with agents four times before they showed up at his apartment May 22.

Attorney Barry Cohen said Monday the elder Todashev fears a cover-up. Agents said they opened fire after Ibragim Todashev became violent.

An Orlando prosecutor is investigating the death. An FBI spokeswoman would not comment. The White House is reviewing the letter.